1. Field of the Invention
The invention relates to a communication system, and more particularly, to a method for detecting loading variation of a power amplifier of a communication system.
2. Description of the Related Art
To prolong battery life of mobile handset devices, the power-efficiency demands from wireless mobile communication systems have become more important. Specifically, a transceiver's most power-hungry device is a power amplifier which has nonlinear characteristics. Meanwhile, modulation of non-constant-envelope signals demands high linearity from a power amplifier. As a result, there is a trade off between linearity and power efficiency in a wireless transmitter.
Furthermore, in a radio frequency (RF) transmission of digital information, sampled data sequences are converted to analog signals and processed, subsequently, by various operations containing unwanted nonlinearities. The primary source of nonlinearity is the power amplifier. The nonlinear behavior of the power amplifier (or other devices) can be compensated for using digital pre-distortion (DPD). That is, the correction signal is a sampled sequence applied prior to the power amplifier to create a corrected signal which compensates for nonlinear modes in the transmitter.